HD Radio: Making the grade

At the
end of November, the National Radio Systems Committee released its
report recommending that the FCC authorize Ibiquity Digital
Corporation's FM In-band On-channel (IBOC) digital radio broadcast
technology as an enhancement to the current analog FM broadcasting
system in the United States. The data reviewed was collected by
Ibiquity, the Advanced Television Testing Center and Dynastat from
eight stations in Annapolis, MD, Baltimore, MD, Columbia, MD, Las
Vegas, New York, San Francisco, and Washington, DC.

The wording used by the NRSC to give its stamp of approval states
that the IBOC system provides a “greatly reduced impact of
multipath interference (for mobile, portable and fixed receivers
alike); superior resistance to co-channel and adjacent channel
interference; support for enhanced data services; [and] improved audio
quality.” The recommendation to the FCC was that an FCC approval
of the system would be “charting the course for an efficient
transition to digital broadcasting with minimal impact on existing
analog FM operation and no new spectrum requirements.”

I think most people were expecting the NRSC to give the thumbs up to
FM IBOC. The concept of an IBOC system has been in the works for the
past 10 years. I believe the NRSC did a thorough and honest job in
making its evaluation. I don't even want to think about what would be
happening right now had the NRSC found IBOC to be less then favorable.
Once the AM report is made, the day will shortly follow when the FCC
makes a ruling on IBOC.

Once word spread that the report was released, I started watching
several discussion lists and talked with several people. IBOC is a
topic that on its own can incite heated debates, and the news of the
report fuels the fires. Some people were quick to point out flaws they
saw in the test data. Since only a few stations broadcast a hybrid IBOC
signal, some feel that the test does not represent a real-world
demonstration for evaluating multipath, co-channel and adjacent channel
interference. Others stressed that the tests used the AAC algorithm for
the audio encoding, while Ibiquity plans to use a form of Lucent's PAC
algorithm for the final system.

Informed, intelligent discussion is vital to coming to an educated
conclusion. While the negative points do raise some good questions,
these are points that have been considered along the way. These are
tests and simulations, which take these factors into account. The key
to the report is that it finds IBOC provides an improvement to the
existing analog system. It does not claim that IBOC is the perfect
system.

We are closer to an IBOC DAB standard, but we're not there yet. The
promise of digital radio is wonderful. The AM report should be issued
very soon, and I'm confident that the NRSC will also apply its seal of
approval. In the end, the AM band has a more obvious gain than FM in
improved fidelity.

I believe that for IBOC to be adopted by all stations, the FCC must
require its implementation with specific dates to mark its transition.
Without a mandate such as this, IBOC will flounder. The cost to
stations for the hardware alone will be more than most are willing or
able to pay. In addition, stations are still not enlightened with the
licensing fees that will be passed on to them to use the
technology.